1. Field of Invention
The present invention relates to otic formulations and antimicrobial agents and more specifically to otic formulations containing a combination of antimicrobials such as quinolones and silver sulfadiazine. More specifically, the invention relates to treatment of animals with ruptured tympanic membrane.
2. Brief Description of the Prior Art
U.S. Pat. No. 4,404,197 discloses the use of certain quinolones and silver sulfadiazine in treating burns. More specifically, the patent discloses compositions that include silver sulfadiazine and 1-ethyl-6-fluoro-1,4-dihydro-4-oxo-7-(1-piperazinyl)-3-quinolone carboxylic acid or its metal salts, e.g., silver, zinc, cobalt or cerium salts. Distinctly, the patent teaches the use of these compositions in treating burns, and in combating topical, surface or skin infections, including microbial and fungal infections and the like. However, the patent fails to teach or suggest the use of the compositions for otic applications.
U.S. Pat. No. 3,761,590 discloses the use of silver sulfadiazine alone in burn therapy. Silver sulfadiazine, preferably in a water-dispersible hydrophilic carrier, is applied to the burn.
Bogaard et al, Dep. Med. Microbiol., Univ. Limburg, Netherlands discloses the use of silver sulfadiazine cream in treating chronic Pseudomonas infection of the external auditory canal in dogs.
U.S. Pat. No. 5,753,269 discloses an otic composition that is useful in treating otic infections comprising an antimicrobial such as a quinolone or a salt thereof and silver sulfadiazine in a therapeutically effective combination to treat otic infections in animals. It has surprisingly been found that this composition is safe and effective in treating otic infection even in instances of ruptured tympanic membrane. Heretofore, art-known treatments of animals with a ruptured tympanic membrane produced adverse effects such as loss of hearing. It is believed that most antimicrobial compounds (e.g. aminoglycosides) have a toxic effect on the hair cells in the cochlea. Such toxicity manifests in eventual loss of hearing. It is worth noting that these compounds may not have toxicity when applied topically on the skin or into the external ear canal where the tympanic membrane is intact, since this membrane acts as a barrier to direct entry of the antimicrobial into the inner ear. However, in instances where the tympanic membrane is ruptured there is loss of the protective barrier and the rupture may provides a ready access of the compounds to the cochlea, increasing the probability for toxicity.